1. Field of the Invention
The present invention relates to a toner, a developer, a process cartridge, and an image forming apparatus.
2. Description of the Related Art
In addition to a conventional kneading/grinding method, the so-called wet granulation method or chemical toner method (wet granulation method), such as a dissolution suspension method or an emulsification method using an organic solvent and an aqueous solvent, and a suspension polymerization method that conducts polymerization while regulating polymerizable monomer droplets to directly obtain toner particles, an agglomeration method that includes preparing emulsified fine particles and agglomerating the fine particles to obtain toner particles have become used for toner production. An agglomeration method that prepares emulsified fine particles and agglomerates the emulsified fine particles to obtain toner particles is one of the chemical toner methods.
Examples of toners proposed as produced by the agglomeration method include the so-called core/shell toners including an inner component of a resin that is advantageous in heat fixation and an outer component of a resin that covers the outside of the toner and is advantageous in blocking and the like (see Japanese Patent Application Laid-Open (JP-A) No. 2006-91564) and toners that contain a crystalline polyester resin and excel in low-temperature fixability (see JP-A No. 2011-145587).
These toners, however, excel in low-temperature fixability, but on the other hand, hot-offset resistance and heat-resistant storage stability are unsatisfactory.
To overcome this problem, a toner, 50% by mass or less of which is accounted for by a polyester resin, produced by mixing a resin dispersion, the resin dispersion being obtained by dissolving a polyester resin A and wax in a vinyl-based monomer, dispersing the solution in a surfactant-containing aqueous phase, and polymerizing the vinyl-based monomer through the action of a polymerization initiator, a dispersion including a polyester resin B dispersed in an aqueous phase, and a dispersion of colorant particles, agglomerating them, and then raising the temperature to allow the agglomerated particles to coalesce with each other has been proposed as a toner that simultaneously realizes low-temperature fixability and hot-offset resistance (see JP-A No. 2008-70755).
In this proposed toner, however, since the resin particles, after agglomerated, are heated at elevated temperatures, compatibilization occurs between resins that have a high affinity, such as between a polyester resin and a crystalline polyester resin, disadvantageously resulting in lowered heat-resistant storage stability of the toner.
Accordingly, the provision of a toner that simultaneously has all of excellent low-temperature fixability, hot offset resistance, and heat-resistant storage stability, a process for producing the same, and a process cartridge that conducts development with the toner has been desired.